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Danielle a Cat 4; Earl more organized; Northwest Passage opens for 4th year in a row

By: Dr. Jeff Masters, 3:20 PM GMT on August 27, 2010

The Atlantic's first major hurricane of 2010, Hurricane Danielle, has arrived. Danielle finished a steady round of intensification early this morning, peaking as a low-end Category 4 storm with 135 mph winds. Infrared satellite loops show little change in Danielle's intensity over the past 12 hours, and the hurricane may be at its peak intensity. Wind shear remains low, 5 - 10 knots, and sea surface temperatures of 29°C are still warm enough to support some modest additional intensification, though. The first Hurricane Hunter mission is scheduled to investigate Danielle this afternoon, and we'll get a better idea of Danielle's strength then.

Figure 1. True color image of Danielle taken at 12:55pm EDT Thursday, August 26, 2010, by NASA's Aqua satellite.

Intensity forecast for Danielle
The latest SHIPS model forecast predicts that shear will remain low, 5 - 10 knots, through Saturday night, but then rapidly rise to a high 25 - 50 knots Sunday through Tuesday when Danielle encounters strong upper-level winds from a trough of low pressure. Danielle may go through an eyewall replacement cycle today or Saturday, which could weaken the storm to Category 2 strength. More substantial weakening will occur on Sunday, when Danielle encounters the high shear.

Track forecast for Danielle
Danielle wandered off of its northwesterly path over the past few hours and has headed almost due west, but the hurricane should resume a more northwesterly path shortly. A trough of low pressure that is currently moving off the East Coast of the U.S. and Canada should begin pulling Danielle due north Saturday, with the hurricane passing east of Bermuda Saturday night through Sunday. NHC is giving Bermuda just a 12% chance of getting tropical storm force winds of 39 mph or greater from Danielle, and no chance of getting winds 58 mph or greater. The Bermuda Weather Service is predicting 10 - 18 foot waves this weekend for Bermuda's offshore waters. All of the computer models agree on recurvature of Danielle out to sea on Sunday, with the storm missing both Bermuda and Canada. The latest wave forecast from NOAA's Wavewatch III model (which uses the GFS model as its prediction for the position and intensity of hurricanes), calls for waves from Danielle to begin hitting the coast of North Carolina on Saturday. These waves will build to 6 - 9 feet in the offshore waters from Northern Florida to North Carolina by Sunday. The latest near shore water forecast for Cape Hatteras calls for 6 - 8 foot waves Saturday, and 6 - 9 feet on Sunday.

Figure 2. Morning satellite image of Earl.

Tropical Storm Earl
Tropical Storm Earl continues to follow a track very similar to Danielles across the mid-Atlantic. The wind shear analysis from the University of Wisconsin CIMSS group shows low shear of 5 - 10 knots over Earl, and recent satellite imagery shows the storm is slowly growing more organized. More low-level spiral bands have developed this morning, and the storm has assumed a more circular shape. Water vapor satellite images show a large region of dry air from the Sahara lies to the west of Earl, and this dry air will likely be the primary inhibiting factor for development over the next few days. Sea surface temperatures are warm, around 28°C. Earl is too far from land for the Hurricane Hunters to reach, and the first flight into the storm is scheduled for Saturday evening.

Forecast for Earl
The latest SHIPS model forecast for Earl predicts that wind shear will remain low to moderate, 5 - 15 knots, for the next five days. There is a possibility, though, that Earl may see higher shear Saturday night through Sunday, due to strong upper-level winds from the outflow of Hurricane Danielle. SSTs will steadily warm from 28°C on Friday to almost 30°C by Sunday beneath Earl. The storm may cross Danielle's cold water wake at some point, which could interrupt development. Dry air will probably be the main inhibiting factor for Earl over the next three days, though. In combination, these factors should allow for intensification of Earl into a hurricane 3 - 4 days from now. An unknown wild card in this may be the possible interaction with 97L. Several models predict 97L will grow to hurricane strength and move faster than Earl. It is possible the storms could interfere with each other, or have some counterclockwise rotation around a common center, 4 - 6 days from now.

History suggests that a storm in Earl's current location has a 15 - 20% chance of making landfall on the U.S. East Coast, but the long term fate of Earl remains unclear. The storm is being steered by the same ridge of high pressure steering Danielle, and Earl will initially follow a track similar to Danielle. As Earl approaches the central Atlantic 3 - 4 days from now, the storm will encounter a break in the region of high pressure steering it, courtesy of Danielle. This should give enough of a northwestward motion to the storm so that it misses the Lesser Antilles Islands. Earl would then likely continue northwest towards Bermuda. However, if Danielle recurves out to sea faster than expected, this ridge may have time to build back enough to steer Earl over the northern Lesser Antilles Islands. NHC is giving Saint Maarten in the northern Lesser Antilles a 35% chance of receiving tropical storm force winds from Earl, and a 8% chance of getting hurricane force winds.

Figure 3. Morning satellite image of 97L.

It's deja-vu all over again, as a new tropical wave (Invest 97L) off the coast of Africa, south of the Cape Verdes Islands, appears destined to develop into a tropical storm and follow the path of Danielle and Earl. 97L already has a broad, elongated surface circulation, as seen on satellite loops, but only limited heavy thunderstorm activity. The storm is experiencing a moderate 10 - 20 knots of winds shear, is over warm 28°C waters, and is battling a region of dry air associated with the Saharan Air Layer (SAL) to its northwest. The latest SHIPS model forecast calls for shear to drop to the low range, 5 - 10 knots, Saturday through Sunday, and this should allow 97L to organize into a tropical depression. The storm will follow a track very similar to Danielle and Earl westward towards the Lesser Antilles Islands, and the storm should arrive near the northern Lesser Antilles 5 - 6 days from now. A more northwesterly path is likely for 97L as it approaches the Lesser Antilles, as the storm follows a break in the high pressure ridge steering it, created by Danielle and Earl. It currently appears that the Northern Lesser Antilles Islands may be at risk of at least a close brush with 97L, though. Most of the computer models develop 97L into a hurricane five days from now. However, the storm will have to contend with the cold water wakes left behind by both Danielle and Earl. Furthermore, the GFS model is indicating that 4 - 5 days from now, Earl will be a strong hurricane whose upper-level outflow will create high wind shear of 20 - 30 knots over 97L, weakening it. History suggests that a storm in 97L's current location has a 15 - 20% chance of making landfall on the U.S. East Coast. NHC is giving 97L a 70% chance of developing into a tropical depression by Sunday.

Elsewhere in the Tropics
In the Eastern Pacific, Hurricane Frank is headed towards Baja California in Mexico, but is expected to dissipate before getting there.

There are more tropical waves over Africa that will be candidates to develop next week once they emerge over the Atlantic. In particular, a wave near 10N 20E has an impressive circulation.

The Northwest and Northeast Passages are open
The Northwest Passage--the legendary shipping route through ice-choked Canadian waters at the top of the world--melted free of ice last week, and is now open for navigation, according to satellite mosaics available from the National Snow and Ice Data Center and The University of Illinois Cryosphere Today. This summer marks the fourth consecutive year--and fourth time in recorded history--that the fabled passage has opened for navigation. Over the past four days, warm temperatures and southerly winds over Siberia have also led to intermittent opening of the Northeast Passage, the shipping route along the north coast of Russia through the Arctic Ocean. It is now possible to completely circumnavigate the Arctic Ocean in ice-free waters, and this will probably be the case for at least a month. This year marks the third consecutive year--and the third time in recorded history--that both the Northwest Passage and Northeast Passage have melted free, according to the National Snow and Ice Data Center. The Northeast Passage opened for the first time in recorded history in 2005, and the Northwest Passage in 2007. It now appears that the opening of one or both of these northern passages is the new norm, and business interests are taking note--commercial shipping in the Arctic is on the increase, and there is increasing interest in oil drilling. The great polar explorers of past centuries would be astounded at how the Arctic has changed in the 21st century.

Figure 4. Arctic sea ice extent image for August 24, 2010, as compiled by The University of Illinois Cryosphere Today. The northern route (Western Parry Channel) through the Northwest Passage was completely clear of ice, as was the Northeast Passage. The southern route through the Northwest Passage was still partially blocked.

What caused the opening of the Northwest and Northeast Passages?
The remarkable thinning of Arctic sea ice in recent years has left behind a very thin layer of mostly 1-year old ice in the Arctic, highly vulnerable to rapid melting. As I describe in detail in wunderground's sea ice page, this thinning was mostly due to natural wind pattern in the 1990s, much warmer than average ocean waters invading the Arctic from both the Pacific and Atlantic Oceans, very warm air temperatures, and deposition of black soot from fires used to clear agricultural land in Europe and air pollution originating in industrialized regions of the Northern Hemisphere. This year, Canada experienced its warmest winter in history, and record warm temperatures were observed during spring over the Western Canadian Arctic. Spring 2010 was the warmest in the region since 1948; some regions of the Western Canadian Arctic were more than 6°C (11°F) above average. These warm conditions helped break the ice up early in the Northwest Passage. Warm conditions continued this summer over both the Northwest and Northeast Passages, with temperatures averaging 1 - 2°C above average over the majority of the region. As observed in previous years, contributing to this year's melt was the presence of much warmer than average ocean waters invading the Arctic from both the Pacific and Atlantic Oceans, and the deposition of black soot on the ice, which absorbs sunlight and heats up the ice. Lack of sunshine and natural wind patterns this summer helped counteract the melting, though, compared to the record melt year of 2007. Still, 2010 is on track come in 2nd or 3rd place for the lowest summertime Arctic sea ice extent on record. The past six years have had the six lowest Arctic ice extents on record, and this summer's melting season took a huge toll on the amount of thick, multi-year old ice, according to the National Snow and Ice Data Center. Modeling results from the University of Washington Polar Science Center (Figure 5) suggest that the volume of Arctic sea ice is at a record low for this time of year. The loss of so much old, thick ice this year makes it increasing likely that Arctic sea ice will suffer a record retreat that surpasses 2007's, sometime in the next ten years. We are still on track to see the Arctic sea ice completely disappear in summer by 2030, as predicted by a number of Arctic sea ice experts.

Figure 5. Arctic sea ice volume as computed by the PIOMAS model of the University of Washington Polar Science Center.

When was the last time the Northwest and Northeast Passages melted free 3 consecutive years?
The first recorded attempt to find and sail the Northwest Passage occurred in 1497, and ended in failure. The thick ice choking the waterways thwarted all attempts at passage for the next four centuries. While we cannot say for certain the Northwest Passage did not open between 1497 and 1900, it is highly unlikely that a string of three consecutive summers where both the Northwest and Northeast Passage opened would have escaped the notice of early mariners and whalers, who were very active in northern waters. We can be sure the Northern Passages were never open between 1900 - 2005, as we have detailed ice edge records from ships (Walsh and Chapman, 2001). A very cold period dominated northern latitudes during the 1600s, 1700s, and 1800s, known as "The Little Ice Age", further arguing against an opening of the Northern Passages during those centuries. The Northern Passages may have been open at some period during the Medieval Warm Period, between 900 and 1300 AD. Temperatures in Europe were similar, though probably a little cooler, than present-day temperatures. However, the Medieval Warm Period warmth was not global, and it is questionable whether or not sections of the Northern Passages along the Alaskan, Canadian, and Russian shores shared in the warmth of the Medieval Warm Period. So, a better candidate for the last previous multi-year opening of the Northern Passages was the period 6,000 - 8,500 years ago, when the Earth's orbital variations brought more sunlight to the Arctic in summer than at present. Funder and Kjaer (2007) found extensive systems of wave generated beach ridges along the North Greenland coast that suggested the Arctic Ocean was ice-free in the summer for over 1,000 years during that period. Prior to that, the next likely time the Northern Passages were open was during the last inter-glacial period, 120,000 years ago. Arctic temperatures then were 2 - 3 degrees Centigrade higher than present-day temperatures, and sea levels were 4 - 6 meters higher. It is possible we'll know better soon. A new technique that examines organic compounds left behind in Arctic sediments by diatoms that live in sea ice give hope that a detailed record of sea ice extent extending back to the end of the Ice Age 12,000 years ago may be possible (Belt et al., 2007). The researchers are studying sediments along the Northwest Passage in hopes of being able to determine when the Passage was last open.

But Antarctic sea ice is at a record high!
Climate change contrarians like to diminish the importance of Arctic sea ice loss by pointing out that in recent years, Antarctic sea ice extent has hit several record highs, including in July of 2010. They fail to mention, though, the fact that ocean temperatures in the Antarctic sea ice region have warmed significantly in recent decades--and faster than the global average temperature rise! So how can sea ice increase when ocean temperatures are warming so dramatically? This topic is discussed in detail by one of my favorite bloggers, physicist John Cook over at skepticalscience.com. In his words:

"There are several contributing factors. One is the drop in ozone levels over Antarctica. The hole in the ozone layer above the South Pole has caused cooling in the stratosphere (Gillet 2003). A side-effect is a strengthening of the cyclonic winds that circle the Antarctic continent (Thompson 2002). The wind pushes sea ice around, creating areas of open water known as polynyas. More polynyas leads to increased sea ice production (Turner 2009).

Another contributor is changes in ocean circulation. The Southern Ocean consists of a layer of cold water near the surface and a layer of warmer water below. Water from the warmer layer rises up to the surface, melting sea ice. However, as air temperatures warm, the amount of rain and snowfall also increases. This freshens the surface waters, leading to a surface layer less dense than the saltier, warmer water below. The layers become more stratified and mix less. Less heat is transported upwards from the deeper, warmer layer. Hence less sea ice is melted (Zhang 2007). "

This counter-intuitive result shows how complicated our climate system is. Climate change contrarians are masters at obscuring the truth by taking counter-intuitive climate events like this out of context, and twisting them into a warped but believable non-scientific narrative. Lawmakers tend to hear a lot of these narratives, since the lobbying wings of the oil and gas industry spent $175 million last year to help convince Congress not to regulate their industry. This number does not include the tens of millions more spent by the U.S. Chamber of Commerce, National Association of Manufacturers, coal industry, and other business interests intent upon stymying legislation that might cut into profits of the oil, coal, and gas industry. For comparison, the lobbying money spent by environmental groups in 2009 was approximately $22.5 million. Spending for PR efforts aimed at influencing opinion on climate change issues probably has a similar disparity. This is a major reason why you may have heard, "Hey, Antarctic sea ice is increasing, so why worry about Arctic sea ice loss?"

Diminishing the importance of Arctic sea ice loss by calling attention to Antarctic sea ice gain is like telling someone to ignore the fire smoldering in their attic, and instead go appreciate the coolness of the basement, because there is no fire there. Planet Earth's attic is on fire. This fire is almost certain to grow much worse. When the summertime Arctic sea ice starts melting completely a few years or decades hence, the Arctic will warm rapidly, potentially leading to large releases of methane gas stored in permafrost and in undersea "methane ice" deposits. Methane is 20 - 25 times more potent than CO2 at warming the climate, meaning that the fire in Earth's attic will inexorably spread to the rest of the globe. To deny that the fire exists, or that the fire is natural, or that the fire is too expensive to fight are all falsehoods. This fire requires our immediate and urgent attention. Volunteer efforts to fight the fire by burning less coal, oil, and gas are laudable, but insufficient. It's like trying to fight a 3-alarm blaze with a garden hose. Every time you reduce your use of oil, gas, or coal, you make the price of those fuels cheaper, encouraging someone else to burn them. Global warming will not slow down until Big Government puts a price on oil, coal and gas--a price that starts out low but increases every year. This can be done via emissions trading, a "fee and dividend" approach, or other means. People are rightfully mistrustful of the ability of Big Government to solve problems, but we don't have a choice. The alternative is to geoengineer our climate--an extremely risky solution. It is time to pay the big bucks and send out the fire engines, before the conflagration gets totally out of control. Consider the Great Russian Heat Wave of 2010 and the Pakistani floods of 2010 a warning. These sorts of extreme events will grow far more common in the decades to come, because of human-caused climate change.

Belt, S.T., G. Masse, S.J. Rowland, M. Poulin, C. Michel, and B. LeBlanc, "A novel chemical fossil of palaeo sea ice: IP25", Organic Geochemistry, Volume 38, Issue 1, January 2007, Pages 16-27.

Funder, S. and K.H. Kjaer, 2007, "A sea-ice free Arctic Ocean?", Geophys. Res. Abstr. 9 (2007), p. 07815.

Walsh, J.E and W.L.Chapman, 2001, "Twentieth-century sea ice variations from observational data", Annals of Glaciology, 33, Number 1, January 2001 , pp. 444-448.

Zhang, J.L., 2006, "Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions", Journal of Climate 20, Number 11, pp 2515-2529.

The Manufactured Doubt Industry and the hacked email controversy, a blog post I did in November 2009.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.